Radio apparatus



March 25, 1930; R. c. DA COSTA RADI O APPARATUS F Filed April 24, 1928 11v VENTOR M1: {9. 24km MQ KBW -1 A TTORNEY Patented .Mar. 25, 1930 PATENT OFFICE ROBERT 0. DA COSTA, OF PHILADELPHIA PENNSYLVANIA, ASSIGNOR TO ATWATEB KENT MANUFACTURING COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A COB- POBATION OF PENNSYLVANIA RADIO APPARATUS Application filed April 24,

My invention relates to radio freqdency inductances,particularly as utilizedinradio frequency amplifier stages of radio receiving apparatus, tunable to the same wave lengths throughout a range of wave lengths.

'In quantityproduction of radio apparatus utilizing cascaded tuned circuits, particularly coupled by thermionic amplifier tubes, coupling transformers are classified according to their turn ratio, as determined by the circuit or stage for which they are constructed, and each class is divided into groups or sub-classes of coils having substantially the same electrical characteristics, as of inductance; the coils of the differentclasses and of the corresponding group or sub-class of each class being associated with substantially identical tuning devices, as for example, condensers, preferably of the striaght-line capacity type, having the same rate of change of capacity, to comprise end of the supporting form; more particu circuits tunable from one wave lengthto another wave length solely by movement of the adjustable elements of the tuning devices to equal extents. y

In accordance with my invention, to facili tate replenishment of groups of the classes, the forms or tubes upon which the coils are wound are each provided at one end .with a plurality of holes, circumferentially spaced, at a selected one of which, during a winding operationis securedlits conductor or wire, to determine within a fraction of a turn, the

number of convolutions of a completed coil whose other end is secured to a fixed point, as provided by a single aperture, at the opposite larly and preferably, the forms, of suitable insulating material, are accurately machined, as by a. grinding operation, to uniform diameter to limits of tolerance within which the transformers, when associated with substantially similar condensers comprise circuits tunable within a given range of wave lengths.

My invention further resides in the method and features, of construction hereinafter described and claimed.

For the purposes of explanation, reference is to be had to the accompanying drawings, in whichz Figs. 1 to 8 inclusive illustrate the succes- 1928. Serial No. 272,385."

sive steps of-constructing a transformer in accordance with my invention.

Fig. 9 is a completed, modified form of transformer.

Referring to Figs. 1 to 7, the coil forms 1, of suitable insulating material, as bakelite, fiber, or the like and preferably tubular in shape, are provided, at least at one end, with a plurality of circumferentially and preferably equally spaced holes 2, and at the other end with a single hole3. Additional holes 4 are provided for purposes hereinafter referred to, Preferably, the coil forms 1 before or after punching of certain or all of the difi'erent holes are accurately machined, as by a grinding operation, to uniform diameter, the maximum variation between the diameters of separate forms being suitably narrow, as for example about .004 of an inch.

Starting at either end, a wire or conductor w is secured to the coil form 1 as by looping it through hole 3, or a selected one of the holes 2, and winding a predetermined numfractional part of a turn bein determined by the position of the selected ole 4 with respect to the hole 3 at the opposite end of the coil. After the winding operation, the coils are preferably giyen a coating of suitable material, for example collodion,'as by a dipping or brushing operation, to retain the turns of the coil 5 in place. After the coating of retaining material has sufficiently set, terminal clips are secured as by riveting, to the coil of Fig. 3, in the holes 4, 4 and a hole 2, "at the upper end of the coil form and to the hole 3 at the opposite end thereof. The ends of the winding 5 are scraped clean of insulation and temporarily secured to oppositely disposed clips, as terminal 8 secured in hole 3 and terminal 9 secured in a hole 2. The lower end of the wire w instead of being se cured to a clip 8 at the lower end of the coil her 'of complete turns upon the form, the

form may, be anchored at the lower end, by

\looping the wire through the hole 3 and thence to the upper end of the coil where it may be secured to a clip riveted in place in a manner similar to the other terminals, as in Fig. 9.

A strip 8 of suitable insulating material, as

varnished silk, may be wound on the coil 5 near the upper end thereof and a second coil 10. of relatively few turns is wound over the strip and retained by dabs d of a quick setting wax at points180 degrees apart, preferably one of the dabs holds the free ends of the coil in positionand insulates the end which crosses over the wound coil. The ends of the coil 10 are then cleaned and connected respectively to the terminal tips 11 secured in the holes 4. The ends'of the coils 5 and 10 'are then soldered to the clips to which they are temporarily secured as above described. The completed coil is then dipped in a suitable compound, as lacquer, to protect the windings from mechanical abrasions and to render it moisture-proof. Thereafter flexi ble leads 15 of different colors for purposes of identification are soldered to the project-- ing ends of the terminal clips and these wires which. are of predetermined lengths are first according to their number. of primary turns which is determined by the stage of the completed amplifier with which they are to be associated. The coils of each class are then grouped according to the measured inductance of their'respective coils 5. In the assembly of an apparatus, the radio frequency trans ormers, each of a required class, having the proper number of primary turns, and of the corresponding group of the classes, that is, having substantially the same inductance, are associated respectively with tuning condensers, having the same rate of change of capacity, and preferably of the straightline capacity type. v

' The rotors of the tuning condensers may be and are preferably mechanically connected to eflect simultaneous tuning of the cascaded circuits by a. single control knob, drum or dial. After assembly and wiring of the amplifier,

and when single dial control of the tuning condensers is desired, the rotors or adjustable elements of the variable condensers are independently and'relatively adjusted until all the tuned circuits are responsive to the same frequency or wave length. The several ad- I justable elements or condenser rotors are then positively and mechanically connected to ef-.

fect their movement in unison. I By constructing the transformers as above and associating selected groups thereof with tuning condensers as described, true single dial operation of radio receiving apparatus is effected, without the necessity of providing additional trimming condensers, or of modifying structurally the individual tuning condensers themselves.

In quantity production of apparatus, as the supply of coils of any group of a class approaches depletion, to replenish the same it is only necessary to specify that coils be wound terminating at a specified one of the holes 2 of the unwound coil forms.

It will be readily understood that all of the operations above described are not necessarily effected in the sequence recited or that all operations are necessary. For example, the coil 10 may be omitted, if it is desired to utilize a single inductance, for example as an auto transformer, and that the primary if used may lie in the plane of the coil or secondary 5 instead of being superimposed thereon. Further, the flexible leads 15 may be soldered to the terminal clips before riveting of the latter to the coil form, and all soldering may be done at one operation, that I is, the ends of the coils 5 and 10 and the flexible leads may be. soldered to the terminal clips without the intervention of the lacquering operation. It is also within the scope of my invention} to omit the clips and leads and.

a leave the ends of the coils secured in the holes in the coil form and of sufiicient length to use them directly as leads, preferably with flexlble tubes, of suitably different colors, and of insulating material slipped over the free ends. What I claim is: a

prising a tubular form machined to uniform, predetermined diameter, a plurahty 6f circumferentially spaced apertures at one end of 1. An air-core, radio frequency coil comsaid form and at least one aperture at the other end thereof, and conductor wound on said form between a selected aperture of said plurality of spaced apertures and said one aperture.

2. An air-core, radio frequency @011 comprising a. tubular form ground to uniform,j

predetermined diameter, a plurality of circumferentially spaced apertures at one end of said form and at least one aperture at the other end thereof, and a coil upon said form terminating at a selected aperture of said plurality of spaced apertures, and at saidnne aperture respectively. Y j

3. An air-core, radio frequency transformer comprising a form having a series of circumferentially spaced apertures at one end thereof and at least one aperture at the other end, a coil terminating, at a selected aperture of said series of apertures and sa1d one aperture, and a second coil terminating at a pair of remain ng apertures ofsa1d semes. I

4. An air-core, radio frequency transformer comprising a tabular form machined to uniform predetermined diameter, a series of circumferentially spaced apertures at one end of said form and at least one aperture at the other end thereof, a secondary coil terminating at a selected aperture of said series and at said one aperture, and a primary coil terminating at a pair of remaining apertures of said series.

5. An air-core radio frequency coil comprising a form having a series of circumferentially spaced terminal points, and at least one other terminal point, and a conductor Wound on said form between said one terminal point and such of said series of terminal points as to procure an inductance of standard magnitude.

6. An air-core radio frequency transformer comprising a form having a series of circumferentially spaced terminal points, and at least one other terminal point, a coil terminating at said one terminal point and at such of said series of terminal .points as to procure an inductance of standard magnitude, and a second coil terminating at another terminalpointof said series.

ROBERT C. DA COSTA. 

